Which of the following most logically completes the argument below?
NowNews, although still the most popular magazine covering cultural events in Kalopolis, has recently suffered a significant drop in advertising revenue because of falling circulation. Many readers have begun buying a competing magazine that, at 50 cents per copy, costs less than NowNews at $1.50 per copy. In order to boost circulation and thus increase advertising revenue, NowNews's publisher has proposed making it available at no charge, but this proposal has a serious drawback, since ___________.